1. Field of the Invention
The present invention relates generally to magnetoresistive (MR) sensor elements employed within magnetic data storage and retrieval. More particularly, the present invention relates to methods for fabricating with enhanced electrical and magnetic properties magnetoresistive (MR) sensor elements employed within magnetic data storage and retrieval.
2. Description of the Related Art
The recent and continuing advances in computer and information technology have been made possible not only by the correlating advances in the functionality, reliability and speed of semiconductor integrated circuits, but also by the correlating advances in the storage density and reliability of direct access storage devices (DASDs) employed in digitally encoded magnetic data storage and retrieval.
Storage density of direct access storage devices (DASDs) is typically determined as areal storage density of a magnetic data storage medium formed upon a rotating magnetic data storage disk within a direct access storage device (DASD) magnetic data storage enclosure. The areal storage density of the magnetic data storage medium is defined largely by the track width, the track spacing and the linear magnetic domain density within the magnetic data storage medium. The track width, the track spacing and the linear magnetic domain density within the magnetic data storage medium are in turn determined by several principal factors, including but not limited to: (1) the magnetic read-write characteristics of a magnetic read-write head employed in reading and writing digitally encoded magnetic data from and into the magnetic data storage medium; (2) the magnetic domain characteristics of the magnetic data storage medium; and (3) the separation distance of the magnetic read-write head from the magnetic data storage medium.
With regard to the magnetic read-write characteristics of magnetic read-write heads employed in reading and writing digitally encoded magnetic data from and into a magnetic data storage medium, it is known in the art of magnetic read-write head fabrication that magnetoresistive (MR) sensor elements employed within magnetoresistive (MR) read-write heads are generally superior to other types of magnetic sensor elements when employed in retrieving digitally encoded magnetic data from a magnetic data storage medium. In that regard, magnetoresistive (MR) sensor elements are generally regarded as superior since magnetoresistive (MR) sensor elements are known in the art to provide high output digital read signal amplitudes, with good linear resolution, independent of the relative velocity of a magnetic data storage medium with respect to a magnetoresistive (MR) read-write head having the magnetoresistive (MR) sensor element incorporated therein.
Within the general category of magnetoresistive (MR) sensor elements, magnetoresistive (MR) sensor elements whose operation is predicated upon a giant magnetoresistive (GMR) effect are presently of considerable interest insofar as those magnetoresistive (MR) sensor elements typically exhibit enhanced levels of magnetoresistive (MR) resistivity sensitivity (i.e. a higher magnetoresistive (MR) coefficient, dR/R) in comparison with magnetoresistive (MR) sensor elements whose operation is predicated upon magnetoresistive (MR) effects other than the giant magnetoresistive (GMR) effect. The giant magnetoresistive GMR) effect is understood by a person skilled in the art to be exhibited by a magnetoresistive (MR) sensor element fabricated employing a series of ferromagnetic layers having interposed therebetween a series of non-magnetic conductor spacer layers, where the thicknesses of each non-magnetic conductor spacer layer within the series of non-magnetic conductor spacer layers is chosen such that adjacent ferromagnetic layers within the series of ferromagnetic layers are magnetically coupled and biased anti-parallel.
Magnetoresistive (MR) sensor elements exhibiting enhanced magnetoresistive (MR) resistivity sensitivity are desirable within the art of magnetoresistive (MR) sensor element fabrication since such enhanced magnetoresistive (MR) resistivity sensitivity clearly inherently allows for detection within a magnetic data storage media of weaker magnetic signals with increased linear density and thus also inherently allows for an increased areal density of the magnetic data storage medium within a magnetic data storage enclosure which employs the magnetoresistive (MR) sensor element which exhibits the enhanced magnetoresistive (MR) resistivity sensitivity.
A typical commercial embodiment of a magnetoresistive (MR) sensor element whose operation is predicated upon the giant magnetoresistive (GMR) effect is a spin-valve magnetoresistive (SVMR) sensor element. Spin-valve magnetoresistive (SVMR) sensor elements typically employ a pair of ferromagnetic layers separated by a non-magnetic conductor spacer layer, where a first ferromagnetic layer within the pair of ferromagnetic layers is additionally magnetically pinned through contact with a hard magnetic material layer to provide a fixed magnetization angle between a first magnetization direction within the magnetically pinned first ferromagnetic layer and a second magnetization direction within the second ferromagnetic layer which is un-pinned. The un-pinned second ferromagnetic layer is alternatively referred to as a free ferromagnetic layer. The giant magnetoresistive (GMR) effect within a spin-valve magnetoresistive (SVMR) sensor element is predicated upon differential electron scattering trajectories within the spin-valve magnetoresistive (SVMR) sensor element incident to magnetic data recording media biasing of a free ferromagnetic layer with respect to a magnetically pinned ferromagnetic layer within the spin-valve magnetoresistive (SVMR) sensor element.
Although magnetoresistive (MR) sensor elements, including spin-valve magnetoresistive (SVMR) sensor elements, are thus well known in the art of magnetic data storage and retrieval, it is nonetheless important within the art of magnetic data storage and retrieval that magnetoresistive (MR) sensor elements are fabricated with enhanced electrical and magnetic properties.
It is thus towards the goal of fabricating for use within magnetic data storage and retrieval magnetoresistive (MR) sensor elements, such as spin-valve magnetoresistive (SVMR) sensor elements, while fabricating the magnetoresistive (MR) sensor elements with enhanced electrical and/or magnetic properties, that the present invention is directed.
Various magnetoresistive (MR) sensor elements and methods for fabricating magnetoresistive (MR) sensor elements, including but not limited to magnetoresistive (MR) sensor elements whose operation is predicated upon a giant magnetoresistive (GMR) effect, have been disclosed within the art of magnetoresistive (MR) sensor element fabrication.
For example, Krounbi et al., in U.S. Pat. No. 4,782,414, discloses a magnetoresistive (MR) sensor element where a trackwidth of a magnetoresistive (MR) layer within the magnetoresistive (MR) sensor element is defined by other than a separation distance of a pair of patterned conductor lead layers formed contacting the magnetoresistive (MR) layer within the magnetoresistive (MR) sensor element. Within the magnetoresistive (MR) sensor element the trackwidth of the patterned magnetoresistive (MR) layer is instead determined by a linewidth of a patterned dielectric layer formed upon the patterned magnetoresistive (MR) layer prior to forming contacting the patterned magnetoresistive (MR) layer and the patterned dielectric layer the pair of patterned conductor lead layers.
In addition, Chen et al., in U.S. Pat. No. 5,491,600, discloses a magnetoresistive (MR) sensor element having incorporated therein a patterned conductor lead layer structure with enhanced mechanical strength and reduced surface topography with respect to a magnetoresistive (MR) layered structure within the magnetoresistive (MR) sensor element. To realize the foregoing objects, the magnetoresistive (MR) sensor element employs a patterned conductor lead layer structure formed of interleaved layers of refractory metal layers and highly conductive metal layers, where the patterned conductor lead layer structure abuts a sidewall of the magnetoresistive (MR) layered structure within the magnetoresistive (MR) sensor element.
Further, Jennison, in U.S. Pat. No. 5,658,469, discloses a method for forming, with a re-entrant profile, a patterned photoresist layer which may be employed as a lift off mask for forming patterned layers when fabricating magnetoresistive (MR) sensor elements. The method employs a patterned photoresist layer formed upon a substrate, an upper portion of which patterned photoresist layer is cross-linked and insolubilized with respect to a solvent, while a lower portion of which patterned photoresist layer is soluble with respect to the solvent, such that when developed within the solvent there is formed within the patterned photoresist layer a reentrant profile with respect to the substrate.
With respect more particularly to magnetoresistive (MR) sensor elements whose operation is predicated upon a giant magnetoresistive (GMR) effect, Gill, in U.S. Pat. No. 5,666,248, discloses a spin-valve magnetoresistive (SVMR) sensor element wherein there is avoided completely the use of an antiferromagnetic pinning material layer for magnetically pinning a pinned ferromagnetic layer within the spin-valve magnetoresistive (SVMR) sensor element. The spin-valve magnetoresistive (SVMR) sensor element instead employs a sense current assisted ferromagnetic coupling of a free ferromagnetic layer and the pinned ferromagnetic layer within the spin-valve magnetoresistive (SVMR) sensor element, along with a pair of ferromagnetic flux guides formed at a pair of opposite edges of the spin-valve magnetoresistive (SVMR) sensor element and including an air bearing surface edge of the spin-valve magnetoresistive (SVMR) sensor element.
Similarly, Ravipati et al., in U.S. Pat. No. 5,739,990, discloses a spin-valve magnetoresistive (SVMR) sensor element with an improved electrical bias structure of the spin-valve magnetoresistive (SVMR) sensor element and a comparatively low resistivity of the spin-valve magnetoresistive (SVMR) sensor element. The spin-valve magnetoresistive (SVMR) sensor element employs a pair of patterned conductor lead layers laterally abutting a ferromagnetic layer within the spin-valve magnetoresistive (SVMR) sensor element, where the patterned conductor lead layers have formed thereover and contacting a top surface of the ferromagnetic layer a pair of longitudinal magnetic biasing layers which define a trackwidth of the spin-valve magnetoresistive (SVMR) sensor element.
Finally, Uno et al., in U.S. Pat. No. 5,772,794, disclose a method for fabricating a spin-valve magnetoresistive (SVMR) sensor element while optimally preserving a magnetic anisotropy of a ferromagnetic layer within the spin-valve magnetoresistive (SVMR) sensor element. The method realizes the foregoing object by employing when fabricating the spin valve magnetoresistive (SVMR) sensor element a final thermal annealing of the spin valve magnetoresistive (SVMR) sensor element at an appropriate temperature and extrinsic magnetic bias field.
Desirable in the art of magnetoresistive (MR) sensor element fabrication are additional methods which may be employed for forming magnetoresistive (MR) sensor elements, such as spin-valve magnetoresistive (SVMR) sensor elements, with enhanced electrical and/or magnetic properties.
It is towards that object that the present invention is directed.